diff --git a/llvm/cmake/modules/HandleLLVMOptions.cmake b/llvm/cmake/modules/HandleLLVMOptions.cmake
--- a/llvm/cmake/modules/HandleLLVMOptions.cmake
+++ b/llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -481,6 +481,10 @@
 
   append("/Zc:inline" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
 
+  # Enable standards-conforming preprocessor.
+  # https://learn.microsoft.com/en-us/cpp/build/reference/zc-preprocessor
+  append("/Zc:preprocessor" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+
   # Some projects use the __cplusplus preprocessor macro to check support for
   # a particular version of the C++ standard. When this option is not specified
   # explicitly, macro's value is "199711L" that implies C++98 Standard.